If you are looking for the easy way, the answer is Amtrak. One train---from Center City to Midtown. Buses can be frustrating and uncomfortable if you are sitting in bumper-to-bumper traffic on the New Jersey Turnpike with limited air conditioning.....I've done those Chinatown buses---AC is sometimes there, sometimes not.

You didn't ask for the least expensive; you asked the easiest. There are plenty of trains between Philly and NYC. If you get to the station early enough, you can get a seat. That too I've done before.